in which we distinguished symmetric (\(\sim \lbrace J_kJ_i\rbrace \equiv J_kJ_i+J_iJ_k\) ) and antisymmetric (gyrotropic, \(\sim J_kJ_i-J_iJ_k=\imath \varepsilon _{kil}J_l\) ) parts (here, \(\varepsilon _{kil}\)  is the Levi-Civita tensor).
After such a simplification, the expression for the susceptibility \(\alpha \)  acquires the form of a quantum mean value of the tensor observable with the operator \(\sim J_kJ_i\)  in the state with the density matrix \(\rho _0\) .
The appropriate superpositional wavefunction \(\Psi \)  (it contains only the components related to the ground multiplet) satisfies the Schrödinger equation \(\imath \dot{\Psi }=H_0\Psi = \omega _{1L}J_z\Psi \)  and is defined by the formula: \(\Psi (t)=\exp ({-\imath \omega _{1L}J_zt})\Psi (0)\) .
Since the operator \(\exp ({-\imath \omega _{1L}J_zt})\)  is the operator of rotation by the angle \(\omega _{1L}t\)  around the \(z\)  axis [1]}, the function \(\Psi (t)\)  represents the function \(\Psi (0)\) , rotating around the magnetic field with the angular frequency \(\omega _{1L}\) .
This rotation is accompanied by `rotation' of the tensor \(\alpha _{ik}\sim \mathop {\rm Sp} \rho _0 J_kJ_i= \langle \Psi |J_kJ_i|\Psi \rangle \)  [2]}, and the noise signal detected in our experiments can be understood as a result of scattering of the probe beam by a quasi-point anisotropic system rotating with the Larmor frequency \(\omega _{1L}\)  around the magnetic field.
If we substitute Eq. (REF ) into (REF ), we obtain for the complex polarimetric signal \(\delta u\)  the following expression
\(\delta u= {\pi kd^2\over \hbar }|A_0({\bf R})|^2 f(t),\) 
